This video image provided by WFAA-TV shows injured people being treated on the flood-lit the high school football field turned into a staging area after the blast in West Texas Wednesday April 17, 2013. (AP Photo/WFAA-TV)

wfaa-tv

Firefighters use flashlights to search a destroyed apartment complex near a fertilizer plant that exploded earlier in West, Texas, in this photo made early Thursday morning, April 18, 2013. (AP Photo/LM Otero)

AP

All that remains of home is a fire place as it smolders after it was leveled near a fertilizer plant that exploded earlier in West, Texas, in this photo made early Thursday morning, April 18, 2013. (AP Photo/LM Otero)

AP

Firefighters walk next to a destroyed apartment complex near a fertilizer plant that exploded earlier in West, Texas, in this photo made early Thursday morning, April 18, 2013. (AP Photo/LM Otero)

AP

A fire smokes near a fertilizer plant that exploded earlier in West, Texas, in this photo made early Thursday morning, April 18, 2013. (AP Photo/LM Otero)

AP

A person looks on as emergency workers fight a house fire after a nearby fertilizer plant exploded Wednesday, April 17, 2013, in West, Texas. A massive explosion at the fertilizer plant near Waco on Wednesday night injured dozens of people and sent flames shooting into the night sky, leaving the factory a smoldering ruin following a blast that damaged buildings for blocks in every direction. (AP Photo/Waco Tribune Herald, Rod Aydelotte)

Waco Tribune Herald

A firefighter walks past a pickup truck with debris from a storage shed on it at a fertilizer plant in West, Texas after an explosion Wednesday April 17, 2013. A massive explosion at the fertilizer plant near Waco on Wednesday night injured dozens of people and sent flames shooting into the night sky, leaving the factory a smoldering ruin following a blast that damaged buildings for blocks in every direction. (AP Photo/The Dallas Morning News, Michael Ainsworth) MANDATORY CREDIT; MAGS OUT; TV OUT; INTERNET USE BY AP MEMBERS ONLY; NO SALES

Dallas Morning News

An elderly person is assisted at a staging area at a local school stadium following an explosion at a fertilizer plant Wednesday, April 17, 2013, in West, Texas. An explosion at a fertilizer plant near Waco caused numerous injuries and sent flames shooting high into the night sky on Wednesday. (AP Photo/ Waco Tribune Herald, Rod Aydelotte)

Waco Tribune Herald

In this Instagram photo provided by Andy Bartee, a plume of smoke rises from a fertilizer plant fire in West, Texas on Wednesday, April 17, 2013. An explosion at a fertilizer plant near Waco Wednesday night injured dozens of people and sent flames shooting high into the night sky, leaving the factory a smoldering ruin and causing major damage to surrounding buildings. (AP Photo/Andy Bartee) MANDATORY CREDIT: ANDY BARTEE

Andy Bartee

A fire burns at a fertilizer plant in West, Texas after an explosion Wednesday April 17, 2013. (APMichael Ainsworth/The Dallas Morning News)

Dallas Morning News

Emergency workers evacuate elderly from a damaged nursing home following an explosion at a fertilizer plant Wednesday, April 17, 2013, in West, Texas. An explosion at a fertilizer plant near Waco caused numerous injuries and sent flames shooting high into the night sky on Wednesday. (AP Photo/ Waco Tribune Herald, Rod Aydelotte)

Waco Tribune Herald

The remains of a home burn early Thursday morning, April 18, 2013, after a fertilizer plant exploded Wednesday night in West, Texas. The massive explosion killed as many as 15 people and injured more than 160, shaking the ground with the strength of a small earthquake and leveling homes and businesses for blocks in every direction. (AP Photo/LM Otero)